apps,nanos-lite,proc: context switch when syscall

apps/nanos-lite/src/irq.c

@@ -7,7 +7,7 @@ static _RegSet* do_event(_Event e, _RegSet* r) {
   _RegSet *ret = NULL;
   switch (e.event) {
     case _EVENT_TRAP: ret = schedule(r); break;
-    case _EVENT_SYSCALL: ret = do_syscall((uintptr_t *)e.cause); break;
+    case _EVENT_SYSCALL: ret = do_syscall((uintptr_t *)e.cause); ret = schedule(r); break;
     default: panic("Unhandled event ID = %d", e.event);
   }
 

apps/nanos-lite/src/main.c

@@ -25,6 +25,7 @@ int main() {
   init_fs();
 
   load_prog("/bin/pal");
+  load_prog("/bin/hello");
 
   _trap();
 

apps/nanos-lite/src/proc.c

@@ -21,12 +21,22 @@ void load_prog(const char *filename) {
   pcb[i].tf = _make(stack, (void *)entry, NULL);
 }
 
+static int cnt = 0;
+
 _RegSet* schedule(_RegSet *prev) {
-  Log("schedule");
   // when current == NULL at the very beginning, it will not cover
   // any valid data, so it will be safe to write to memory near NULL
   current->tf = prev;
-  current = &pcb[0];
+  if (current == &pcb[0]) {
+    cnt ++;
+    if (cnt == 1000) {
+      current = &pcb[1];
+      cnt = 0;
+    }
+  }
+  else {
+    current = &pcb[0];
+  }
   _switch(&current->as);
   return current->tf;
 }